This invention is related to the sheet post processing device that sorts continuously transported sheets onto several trays.
Previously, a movable tray type with vertically movable trays and a fixed tray type with fixed trays are known to be employed in this type of sheet post processing device. The movable tray type has an outlet in the fixed position to eject continuously transported sheets. Several trays are disposed in a vertically spaced direction and selectively move to the receiving position for the sheets ejected from the outlet. On the other hand, the fixed tray type has several transport paths that transport sheets to the respective tray. By switching those transport paths, sheets are selectively transported onto several trays.
However, among the previous sheet post processing devices, the movable tray type requires a large drive mechanism to move up and down heavily loaded trays due to accumulated sheets. If a sheet is ejected onto a lower tray among several trays that are located in vertically spaced direction, upper trays will significantly move to the top of the sheet infeed expanding large moving space to upper area. On the contrary, the fixed tray type requires several transport paths, complicating and enlarging the composition of the entire device.
There have been devices that transport the sheets that are continuously ejected from a host machine such as a copier or a printer, reverse the transport direction of the sheet, and transport the sheet into the sheet post processing portion of the device that staples and sorts the sheets. Generally, this type of sheet reversing device is incorporated into the sheet post processing device such as a stapler or a sorter.
The previous sheet reversing devices transport each sheet onto the stage, reverse the sheet transporting direction, and transport sheets one by one by converting the trailing end of the sheet to the leading end. After transporting one sheet onto the stage, the device transports the sheet in its reversed transporting direction. Then, after the sheet is transported, the next sheet is transported onto the stage.
However, since the previous sheet reversing device repeats transporting sheets one by one and in a reversed direction on the stage, the next sheet could not be transported onto the stage unless the previously transported sheet on the stage is ejected. Therefore, for example, the sheet reversing device that reverses the sheet ejected from a host machine such as a copier or a printer and transports the sheets into the sheet post processing portion for stapling or sorting takes time. If the sheet is temporarily delayed to be transported into the sheet post processing portion from the stage, the next sheet cannot be transported onto the stage and the host machine such as a copier or a printer has to be temporarily stopped. That is, due to a delay of the movement timing of the transporting destination of the sheet transported from the sheet reversing device, the transportation of the sheets into the sheet reversing device had to be stopped and therefore the speed of sheet processing decreased.